Gear preloading device on pitch change mechanism for oppositely rotating propellers



Jan. l0, 1956 P. M. FREEMAN 2,730,18l

GEAR PRELOADING DEVICE ON FITCH CHANGE MECHANISM F OR OPPOSITELY ROTATING PROPELLERS Filed Jan. 8, 1952 2 Sheets-Sheet l T TORNE' y Mmmm NIIIIIIIIIIMW' -ff JEM. Q p M FREEMAN 2,730,11

GEAR PRELOADING DEVICE ON PITCH CHANGE MECHANISM FOR OPPOSITELY ROTATING PROPELLERS Filed Jan. 8, 1952 2 Sheets-Sheet 2 A POWER PLANT VVE/V70@ PHIL/P IW FEEMAN 7' TORNEI GEAR PRELOADING DEVICE ON PITCH CHANGE MECHANISM FOR OPPSITELY ROTATING PROPELLERS Philip M. Freeman, Farmington, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application January 8, 1952, Serial No. 265,403 lil Claims. (Cl. 170-135.27)

This invention relates to mechanism for preloading gearing and more specically for eliminating back-lash in propeller blade pitch adjusting mechanism.

It is an object of this invention to provide an improved back-lash eliminator.

Another object of this peller pitch adjusting mechanism.

A further object is a simple mechanism preloading a gear train in a pitch changing mechanism to cause movement of the pitch control mechanism outside the propeller to result in a corresponding movement of the pitch changing mechanism on the rotating propeller without lost motion.

A still further object is a simple back-lash eliminator utilizing the effect of centrifugal force to maintain an unreversing load on a gear train.

Other and additional objects will be obvious from the attached specification, claims and drawings in which Fig. l is a longitudinal cross sectional View through a dual-rotation propeller pitch control mechanism partly in section and partly in phantom with the sections taken along arbitrary planes to conveniently illustrate the majority of the operating units.

Fig. 2 is an end View taken Fig. 1 with portions omitted emphasize the invention.

Fig. 3 is a section taken along lines 3 3 showing the eccentrically loaded gear.

Fig. 4 is a general View of a dual-rotation propeller.

The invention has been illustrated herein in a dualrotation pitch-changing mechanism but it should be understood that it could be used in a single rotation propeller or in other rotating mechanism.

Referring to Fig. 1, a dual-rotation propeller is shown having an inboard unit generally indicated at 20, and an outboard unit generally indicated at 22, respectively, each of which include hubs 24 and 26, respectively, and a plurality of blades 28 and 30 mounted for pitch changing movements relative to the hubs. The propeller units are driven by a propeller power plant 4) in opposite directions at a xed ratio or equal speeds by a well-known means omitted herein for convenience. The propeller units and 22 include a mechanism therebetween interconnecting the propeller blades including a housing indicated generally at 44 which normally remains stationary during propeller rotation.

The pitch of the propeller blades 28 and 30 may be varied by uid operated motors such as, for example, illustrated and described in patent application Serial No. 154,857, filed April 8, 1950, by Arthur N. Allen, Jr., now U. S. Patent No. 2,667,229.

In order to properly synchronize and coordinate the pitch changing movements of the blades of the several propeller units, it is desirable to provide a simple yet eilicient interconnecting mechanism between these propeller units. To this end the inboard propeller hub 24 (see Fig. l) is driven by an outer shaft 50, while the outboard propeller hub 26 is driven in the opposite direction by an along the lines 2 2 of to more clearly show and invention is an improved pro- States Patent O rice inner concentric shaft 52. The inboard hub 24 includes a blade interconnecting gear 56 meshing with gears 54 on the base of the blades 28 to synchronize the pitch changing movement of all the blades mounted within the hub 24. The synchronizing gear 56 is connected by means of a gear train (to be described in detail hereinafter) to the distributor valve indicated generally at 60 and located within the outboard hub 26. The distributor valve 60 controls the ow of hydraulic fluid to the pitch changing motors of the propeller blades 30 of the outboard hub 26 as described in detail in the above referred patent application, so that the pitch of the blades 30 will be varied in response to the pitch changing movement of the blades 2S of the inboard hub 24. The present invention relates to mechanism for preloading, or eliminating, the back-lash from this gear trainvso that the pitch of the blades of the outboard propeller will closely follow the pitch of the blades of the inboard propeller. The blade synchronizing gear 56 of the inboard hub 24 includes a forwardly extending sleeve 64 which has a spline connection 65 with a ring gear 66 which in turn meshes with a gear 68 keyed to a shaft 72 journalled within the hub 24. Gear 68 drives another gear 70 by means of the common shaft 72. Gear 70 meshes with a ring gear 74 which is carried by a rearwardly extending portion of a freely rotatable sleeve 76 forming a part of the inter-propeller connecting mechanism contained within the aforementioned housing 44. The sleeve 76 has a forwardly extending portion 78 which carries a ring gear 80. The ring gear 80 is connected with another ring gear 82 of similar diameter by means of a plurality of reversing gears carried by the housing 44. These gears will, as long as the housing remains stationary, impart equal and opposite rotation to the gears 80 and 82. As will be explained later, housing 44 is normally stationary and hence gear 82 will normally be rotated at the same speed as, but in the opposite direction to, gear 80. The reversing gears comprise a gear 280 mounted on a shaft (not shown) which is freely rotatable in bearings carried by the wall 150 of the inter-propeller housing 44. Gear 280 meshes with gear 286 which is fixed to a shaft 288 mounted in bearings 290 in the wall 150 of the inter-propeller housing 44. Gear 286 is axially spaced from gear 80 so as not to interfere therewith. Shaft 288 has a gear 292 fixed thereto to turn with gear 286. Gear 292 meshes with gear 82 to provide the re- Versing connection between ring gear 80 and ring gear 82. This gear train has gears Sii and S2 in opposite directions at equal speeds. This is true when the shafts S0 and 52 are driven in opposite directions at equal speeds but if the driving mechanism for the shafts 5t) or 52 drives these shafts at some other ratio, the reversing gears just described will drive gears 80 and 82 at this other ratio.

The gear 82 is carried by a freely rotatable sleeve 84 which carries a cam track 86 and is located within the rear portion of the hub 26. A cam follower 88 cooperates with a cam track S6 in such a manner that rotation of the sleeve 84 will cause cam follower $8 to rock about its pivot 90 so as to reciprocate the spool 92 of the distributor valve 60. Pressure fluid for the distributor valve and the pitch changing motor is provided by a pump (not shown) which is driven by rotation of the hub 26 as more fully described in application of Earl M. Frankland, Serial No. 162,728, filed May 18, 1950, now U. S. Patent No. 2,679,907 for Stationary Inter-propeller Housing.

The above described gear train connects the propeller blades 28 of the inboard hub 24 with the distributor valve 60 of the outboard hub 26. A similar gear train which will .now be described interconnects the inboard hub 24 with the blades 30 in the outboard hub 26. The blades 30 being normally hydraulically locked by their pitch changing motor, unless the distributor valve is calling for a been described as driving thev change of pitch, serves to anchor one end of the gear train and the hub of the inboard propeller 26 servesto anchor the other end of the gear train about to be described so that the housing 44 is fixed in space and held against rotation.

The blades 30 of the outboard hub 26 arevall geared to the blade synchronizing gear 11% to maintain them in the same relative pitch positions. synchronizing gear 110 is splined to a blade follow-up gear 114 which meshes with gear 116 fixed on shaft 126 which also carries a gear 118 thereon. Gear 11S meshes with idler gear 130 which in turn meshes with gear 134 carried at one end of a freely rotatable sleeve 136 which carries a ring gear 13S at its other end. Gear 13S is connected to a similar gear 14) by means of a reversing gear train. This reversing gear train is similar to the reversing gear train previously described and comprises a gear 300 meshing with gear 138 and supported on a shaft (not shown) in the housing 150 for free rotation. Gear 360 meshes with a gear 310 carried by a shaft 302 journalled in bearings 304 and 305 carried by the walls 150 of the housing 44. Gear 310 also meshes with gear 14) to provide the reversing connection between the gears 138 and 140. Gears 300 and 310 are wide gears and overlap each other so as to mesh with each other in the space between the gears 138 and 14). Ring gear 146 is carried by a freely rotatable sleeve 142 which is splined at 144 to a sleeve 146 fixed to the inboard hub 24 by means of bolts 148.

summarizing the two gear trains connecting the propeller blades of the two oppositely rotating propellers comprises one train connecting the hub 24 of the inboard propeller with the blades 30 of the outboard propeller and another train connecting the blades 28 of the inboard propeller with the distributor valve 60 of the outboard propeller. inthe first train, the gear 140 being splined to the hub 24 is in elfect fixed with respect to the outer drive shaft 50. The gear 13S being geared to the blades of the outboard propeller, which, except when the pitch is being changed, are hydraulically locked with respect to the outboard hub 26 is in effect fixed with respect to the inner shaft 52. The shafts 50 and 52 being geared together inside the engine to rotate at equal and opposite speeds will drive the gears 138 and 140 at equal and opposite speeds so that the reversing gears 300, 310 connecting gears 13S, 140l will rotate on their own axes and have no tendency to rotate around the propeller shaft. These gears 300, 310 will therefore hold the housing in which they are mounted against rotation as long as there is no pitch change in the outboard propeller.

In the other gear train, which is the one which we are interested in in this invention, the gear 80 is geared to the propeller blades of the rear propeller, which, except when there is a pitch change of the propeller, are hydraulically locked to the rear hub 24, so that the gear 80 will in effect be fixed to the hub 24 and shaft 50 and rotatetherewith. The gear S2, however, is freely rotatable. The reversing gears 280, 286 and 292 being mounted on shafts supported in a housing 150 held against rotation by the other gear train, as previously described, will rotate the gear 82 and hence the cam 86 at a speed equal and opposite to that of gear Si). It will be noted that this last gear train has a freely rotatable gear 82 as the last member. As more fully explained in application Serial No. 162,728 referred to above, pitch changing movement of propeller blade 2S will cause movement of gear 82 and the cam S6 attached thereto thus moving distributor valve 60 to change the pitch of the outboard propeller blades which pitch changing movement of the outboard propeller blade will move the gear 138 and hence the support 150 to return the distributor valve 60 to its inactive position.

ItV willY be noted that the gear train connecting the inboard propeller blades 28 with the distributor valve 60 comprises about six sets of meshing gears and that one end of the gear train is free to rotate so that any backlashin this gear train would permit the distributor valve l 60 to oscillate under the effects of vibration and thus cause continuous minute pitch changes of the outboardvpro peller.

ln order to eliminate this backlash and continuously load the gear train connecting the inboard blades 28 with the distributor valve 6i), a gear 320 is mounted for free rotation on a stud 322 secured in a boss 324 forming a part of the hub 26. A snap ring 326 holds the gear in position on stud 322. Gear 320 meshes with gear 328 formed in the outboard flange of the cam groove 36 on the end of slccve 84. Gear 32) is eccentrically weighted as by a weight 330 on one side, A second gear is mounted diametrically opposite the gear 320 to provide a balanced assembly. The weighted portion 330 of the gears 329 are eccentrically located so that centrifugal force acting on the weights due to rotation of the propeller hub will supply sufficient force to continuously urge gear 328 and sleeve 84 in one direction. This force is suficient to load the gear train connecting distributor valve 6i) and blades 23 continuously in one direction and hence remove the effects of backlash. This loading of the sleeve 84 will also tend to move the support 159 and the stationary housing 44 continuously in one direction but movement of housing 44 is prevented by the gear train conecting the inboard hub with the outboard blades. It will be appreciated that the distributor valve 66 and hence the gear 328 always returns to its inactive position after a pitch changing movement and moves only a slight distance each side of the inactive position to initiate pitch changing movements of the outboard propeller. Therefore any movement of the gear 326 would be only a small amount from the position shown in Fig. 2 which is the position they would occupy in the neutral or inactive position of distributor valve 60. it should be undcrstood that if the elimination of backlash is important only in one particular position of the valve 6d, such as the neutral or on speed position, the gears 325) will be positioned so as to load the gear train Whenever the valve is in that position but may, if the movement of gear 328 is sufficient, be moved more than 45 in either direction so as to give no loading or even load the gear train in the opposite direction in valve positions in which the backlash of the gear train is uniimportant. If, however, it is important to load the gear train at all times the ratio of gears 323 and 320 are made such that gears 320 will not have movements of over 45 in either direction from their position as shown in Fig. 2. The weights are therefore always in position to load the gear train in the same direction. The gears 320 are mounted to rotate with the propeller hub about the propeller axis and rotate only slightly on their own axis and then only while pitch of the outboard propeller is being changed, so that the centrifugal force acting on the weights 330 is induced by the rotation of the outboard propeller hub and acts eccentrically of the axis of gears 320. This eccentric force tends to rotate gears 320 and will of course act as long as the outboard propeller is rotating.

From the above it will be apparent that I have provided a mechanism by which a gear train may be preloaded continuously in one direction by centrifugal force induced by rotation of part of the gear train itself.

Although only one embodiment of this invention has been illustrated and described herein, it will be apparent that various changes and modifications may be made in the construction and arrangement of the various parts without departing from the scope of this novel concept.

What it is desired to obtain by Letters Patent is:

l. Means for continuously preloading, in one direction, a gear train having a continuously rotating gear at one end of the train, comprising, a continuously rotating member, means for driving said member at the same speed and in the same direction as said rotating gear, an eccentrically loaded gear meshing with said rotating gear, and mounted for rotation upon and rotation with said rotating member and adjustable means connected with said rotating gear andv carried by said member and adjustable by relative movement of said rotating gear and said member.

2. Means for preloading a gear train having a continuously rotating gear at one end of the train comprising a continuously rotating member, means for driving said member at the same speed and in the same direction as said rotating gear, an eccentrically loaded gear meshing with said rotating gear, and mounted for rotation upon and rotation with said rotating member and adjustable means connected with said rotating gear and carried by said member and adjustable by relative movement of said rotating gear and said member and means at the other end of the gear train for moving said rotatable gear with respect to said member.

3. A backlash eliminating device for a gear train comprising a gear continuously rotating about its axis and forming a part of said train, an eccentrically weighted gear free to rotate about its axis, meshing with said rotating gear, and positioned eccentrically of the axis of said rotating gear, a support for said weighted gear, means for rotating said support in synchronism with and around the axis of said rotating gear, means rotatably supporting said weighted gear upon said support so that centrifugal force continuously tends to rotate said weighted gear in one direction.

4. In combination, a member, a rotatable gear, means including said member for rotating said rotatable gear, a gear train connecting said member with said rotatable gear, a support, means for rotating said support in the same direction and at the same speed as said rotatable gear so as to maintain said support substantially stationary with respect to said gear, an idler gear rotatably mounted on said support and meshing with said rotatable gear, a weight mounted on said idler gear eccentric thereof and normally positioned to one side of a line connecting the axes of said idler and rotatable gears, adjustable means carried by said support and connected With said rotatable gear, means including said gear train for moving said rotatable gear relative to said support for adjusting said adjustable means.

5. Means for preloading a gear train having a rotatable gear at one end of said train and an adjustable gear at the other end of said train, a support rotatable with said gear and substantially stationary with respect to said gear, means for rotating said support, a member pivoted on said support for movement in a plane parallel to the plane of said gear, means operatively connecting said pivoted member with said gear, a weight mounted on said member normally eccentric of a line connecting said pivot and the axis of said gear adjustable means carried by said support and operably connected with said rotatable gear for adjustment by relative movement of said support and said rotatable gear.

6. Means for preloading a gear train having a rotatable gear at one end of said train, a support rotatable with said gear and substantially stationary with respect to said gear, means independent of said gear train for driving said support, a weight supported on said support for movement under the iniuence of centrifugal force induced by rotation of said support and gear outwardly of said gear in the plane of said gear, and means operatively connecting said weight and said gear for urging rotation of said gear in one direction.

7. In combination with a propeller, hydraulic pitch-control mechanism therefor comprising, a control valve rotatable with the propeller, means for actuating the control valve, including a gear train connecting said control valve with a pitch selector and having a gear adjacent said valve and rotatable with said propeller, means for loading said train comprising a member carried by and rotatable with said propeller, means operatively connecting said member with said gear adjacent said valve, and means movable away from said gear, by the action of centrifugal force due to rotation of said propeller, connected with said member for urging said gear in one direction.

8. In a dual rotation propeller, outboard and inboard propeller components adapted to be driven in opposite directions at a iixed speed ratio, pitch changing mechanism comprising a first gear train, including a tirst set of planet gears and a cage, connecting the hub of one component with the blades of the other component and acting to position said cage, a second gear train, including a second set of planet gears and said cage, connecting the blades of said one component and a freely rotatable pitch control element carried by said other component, and a centrifugally actuated weight carried by said other component and operatively connected with said pitch control element to bias said element and said gear train in one direction.

9. In a dual rotation propeller, outboard and inboard propeller components adapted to be driven in opposite directions at a xed speed ratio, pitch changing mechanism comprising a irst gear train, including a iirst set of planet gears and a cage, connecting the hub of one component with the blades of the other component and acting to position said cage, an hydraulic pitch changing motor positioning the blades of said other component, a freely rotatable pitch control element rotatable with said other component, a control valve for said motor, a second gear train, including a second set of planet gears and said cage, connecting the blades of said one component and said element, means connecting said element with said valve, and a centrifugally actuated weight pivoted on said other component and operatively connected with said pitch control element to bias said element and said gear train in one direction.

10. In a propeller having hydraulic pitch control mechanism, a propeller hub, a control valve rotatable with the propeller hub, means for actuating the control valve, including a gear train connecting said control valve with a pitch selector, means for loading said train comprising a member operatively connected with said valve and rotatable with said propeller hub, means operatively connecting said member with the gear of said train adjacent said valve, and a centrifugally actuated weight pivoted on said propeller hub and operatively connected with said member to bias said member and said gear in one direction.

i References Cited in the file of this patent UNITED STATES PATENTS 2,154,359 Sarazin Apr. 11, 1939 2,182,988 Iseler Dec. 12, 1939 2,432,907 Longer Dec. 16, 1947 2,466,775 Martin Apr. 12, 1949 2,514,166 Ratie July 4, 1950 FOREIGN PATENTS 108,379 Australia Sept. 7, 1939 240,259 Great Britain Oct. 1, 1925 

